I was confused, for there was three commas(,) in the original sentence.
So I changed the form of original sentence. Please look at the below.
Did I changed the sentence grammatically?
Original sentence: "In atherosclerosis, small patches of fatty material, composed mostly of cholesterol, form on the inside lining of the arteries."
Transformed sentence:"Small patches of fatty material, composed mostly of cholesterol, form on the the inside lining of the arteries in atherosclerosis."
I get confused if there are more than three commas in the sentence. Because I'm not used to those kinds of sentences.
And sometimes it's hard to find which thing modifies.